Researchers from Yale University suggest an alternative design. Instead of using salt- and freshwater, they buddy up their freshwater with a solution of ammonia and carbon dioxide in water. The osmotic pressure produced can be an order of magnitude higher than that produced with salt solution. Maintaining the difference between the solutions requires only a small amount of heat. Raising the temperature to just 40 °C is enough to evaporate off water from the ammonia-CO2 solution to maintain its concentration. Evaporating water from salt solution is much harder. The evaporated water is then condensed and fed back to the freshwater side of the osmotic engine.

The patent estimates each metre of membrane could produce 250 watts of electrical power, compared to the 4 watts typically produced by an equivalent area in an estuary-based plant.